This invention relates to forming decorative patterns on metallized film, and more particularly, this invention relates to a system and method for forming a pattern on metallized film, such as including plain or holographic metallized films and hot stamp foils, including embossed substrates with or without holograms.
Decorative packaging, currency bills, labels, containers and many other objects used in different applications often display a repetitive pattern on metallized film, often formed as a polymer base layer and a metallized surface, such as copper or aluminum.
Some of these applications include a colored, metallic foil that is hot stamped, in place of ink, onto a substrate or melted onto a print substrate. For example, a hot stamp printing plate could be cast or engraved into a piece of metal and held by a heated fixture. Between the plate and substrate, a hot stamp xe2x80x9cfoilxe2x80x9d (film) with a color or metal transfer ink coated in a thin layer is compressed onto the substrate to transfer the image. The printers could be flatbed platen units, rotary, units, or automatic web feed presses. It is also possible that holograms and/or diffractive images are added for enhanced security.
The use of enhanced security, hot stamp foils for authentication is becoming increasingly popular and is evident when one views many currency bills used in Europe and other countries. The enhanced security hot stamp foils often incorporate a hologram or other optical device, such as a diffraction grating or pattern or a kinegram. These devices allow enhanced protection and authenticity of various documents or plastic cards. Different substances can be used, including PVC, coated papers, textured security or bank note papers, packaging films, textiles, thermosensitive papers, and other similar substrates.
It is also possible to use not only foil stamping methods, but also use embossing techniques with the substrates. For example, a metal plate with a specific image is created and pressed onto the substrate leaving behind an image. This process is different from foil stamping where the image is transferred rather than pressed. Sometimes a holographic xe2x80x9cpatchxe2x80x9d can be created by embossing a hologram onto a hot stamped foil, or a narrow strip hologram can be made from hot stamped foil and applied to a document.
In one process, a printer hot stamps blank foil onto a document and creates a hologram by embossing a holographic image onto blank foil. The holograms can be embossed in-line using a blank foil or embossable substrate. One station could hot stamp chemicals onto the substrate and another station could emboss the image in foil. It is possible to surface coat a substrate with silver and chemicals to make holograms in-line such that hot stamping may not be required when using an embossable substrate.
In one prior art technique, the base layer of a hologram is created by hot stamping foil on a substrate using a rotating, heated, stamping cylinder and associated base roller. The substrate and foil pass between the cylinder and roller. The cylinder includes a raised pad to configure the holographic image. It is also possible to emboss by using a holographic printing place (as a shim), and a rotating, heated, embossing cylinder and rubber-coated base roller. The applied foil with the substrate passes between the cylinder and roller and a raised pad, which is larger in size than the hot stamping pad, comes into contact with the foil to create the holographic image. Demetallization is often used to add further security and design with different levels of transparency.
Holograms are advantageously used because they combat counterfeiting and cannot be copied easily using a photocopier. They are also difficult to scan digitally using computer equipment. Holograms allow validation, especially with hidden and embedded holographic images. It is also possible to use a xe2x80x9ckinegramxe2x80x9d image, such as formed from fine lines of different thicknesses and shapes on a metallized foil. As the angle of light changes, the image of the kinegram also changes, producing the effect of a moving picture that could enhance security.
In one common prior art demetallization system used with packaging, a web of metallized polymer film is printed with a repetitive pattern of etchant-resistant material that has been applied from a gravure roll, corresponding to the pattern desired to be produced on the metallized surface, typically an aluminized or copper surface. An aqueous sodium hydroxide (NaOH) solution having a concentration of up to 25% by weight (NaOH) is applied at a temperature from about 15xc2x0 to about 100xc2x0 C. across the web to contact and etch those areas of the metallized surface that are free of the etchant resistant material. This sodium hydroxide (NaOH) solution remains in contact with the web for about 0.1 to about 10 seconds, depending on the thickness and metal used in the metallized surface to permit the sodium hydroxide to dissolve the aluminum from those areas of the web not having the etchant-resistant material. The material then is washed to remove any excess etchant and etchant by-products.
Usually this type of system uses rollers that feed the web and dips the web into baths of liquid to effect the various steps. Some prior art improvements spray an etchant onto the film. Scrapers remove any etched material. These steps are usually followed by warm water sprays to wash any etchant from the film surface. Afterward, the washed film is hot air dried and chill-roll cooled.
In other prior art systems, a substrate film is printed with a pattern of water-based printing varnish having an etchant dissolved therein, which remains in contact with the metallized surface for a time sufficient to etch the pattern onto the metallized surface. Any excess etchant is washed from the film and dried.
Another improvement has a patterned laminate formed by printing an image of an etchant by gravure roller on a web and laminating the printed web with another web such that the image is sandwiched between the webs in contact with the metallized film. The etchant dissolves the metallized surface in the printed areas to provide a desired pattern. The resulting laminate may be used as a packaging material. Further prior art improvements include selectively demetallizing film in different areas to form a graduated optical density for decorative packaging or even security purposes.
One drawback of many prior art demetallization and pattern forming systems is the repetitive pattern that is consistently applied onto the metallized surface. In decorative packaging, this is acceptable. In other instances, such as the holographic metallized film where security is an issue, it is not acceptable. For example, it may be desirable to form a unique metallized pattern on currency bills or identifying labels instead of the prior art repetitive pattern that is typically applied to some currency bills, and areas of decorative packaging, labels, containers and other items.
It would be advantageous if a demetallization pattern could be uniquely applied by a system and method where a unique and item specific (such as currency bill specific) pattern could be applied individually to successively produced items, such as currency bills, labels, containers and similar items. This pattern could be in a microscopic or macroscopic pattern.
It is therefore an object of the present invention to provide an improved system and method for forming a pattern on plain or holographic metallized film and hot stamp foil, including embossed substrates with or without holograms, which overcomes the disadvantages of the prior art.
It is yet another object of the present invention to provide a system and method that forms an item specific pattern on plain or holographic metallized film and hot stamp foil, enhancing security and identification on currency bills, labels, containers and similar items.
The present invention advantageously provides a system and method for forming an item specific pattern on a metallized surface of plain or holographic metallized film or hot stamp foil, including embossed substrates. The metallized surface is etched into an item specific pattern that can be unique or repetitive, no matter the application or item, such as a currency bill, label, container or similar items.
The system and method of the present invention individually and digitally controls ejection of ink having one of an etchant or etchant-resistant mask material from an ink jet printhead. Control can be performed adequately by a programmable logic controller (PLC) operatively connected to the ink jet printhead, for individually and digitally controlling ejection of the ink and etchant therein through respective ink jets in a programmed and controlled manner. The present invention permits ink jet printing onto a metallized surface with an item specific pattern of ink. When etchant is included with ink, the etchant etches the metallized surface into an item specific pattern. When an etchant-resistant mask is applied, a subsequent etchant is applied, etching those areas not covered by the mask. By digitally controlling the printing of ink with the etchant or etchant-resistant mask material through the ink jet printhead, individual, customized metallized patterns that are item specific can be applied to each article or item, such as a currency bill, label or container. The item specific pattern not only could act as an enhanced security feature, but also could act as an identifying indicia for tracing a currency bill via the pattern.
In one aspect of the present invention, an item specific pattern is etched into a metallized film having a polymer base layer and metallized surface such as an aluminized surface. An ink jet printhead has the plurality of ink jet channels and respective ink jets that receive ink having an etchant or etchant-resistant mask material therein and ejects ink through respective ink jets onto the metallized surface. A controller is operatively connected to the ink jet printhead and individually and digitally controls ejection of ink, such as etchant or etchant-resistant mask material, through the respective ink jets in a programmed, controlled manner for ink jet printing on the metallized surface a pattern of etchant or etchant-resistant mask such that if an etchant, it etches the metallized surface into an item specific pattern that is individual to an item, such as a currency bill, label or container. If an etchant-resistant mask is applied, an etchant is subsequently applied, such as by an etchant bath, for etching those areas that are not covered by an etchant into the surface relief pattern.
A film advancing mechanism advances a plain or holographic metallized film or hot stamp foil along a predetermined path of travel into a demetallization station where the ink jet printhead is located. In one aspect, an ink reservoir holds an ink that includes an etchant or etchant-resistant mask material. The ink reservoir can be an integral part of the ink jet printhead, mounted adjacent the ink jet printhead, or mounted separate as a large ink reservoir or container holding ink and one of etchant or etchant-resistant mask material. Ink is delivered to a smaller reservoir mounted at the ink jet printhead. A washer can be located along this predetermined path of travel for washing excess ink and etchant from the metallized surface after the pattern has been etched on the metallized film.
A printhead mounting assembly can mount the ink jet printhead for angled movement relative to the metallized surface of the plain or holographic metallized film or hot stamp foil for changing the resolution of the ink applied in a pattern based on the angle of the ink jet printhead. In another aspect of the present invention, the ink jet printhead can be a Drop On Demand (DOD) printhead, such as a piezoelectric ink jet printhead. It could also be a Continuous Ink Jet printhead (CIJ).
The system includes a controller, such as a programmable logic controller (PLC), mounted on appropriate boards for implementing the logic and programming necessary to form an item specific pattern for use with currency bills, labels, containers and the like. When the metallized surface is aluminum, the etchant could be a base or acid, and could be sodium hydroxide (NaOH) or a combination of similar etchants.
In another aspect of the present invention, a currency bill, formed from a substrate such as paper, has a metallization layer that has been etched into an item specific (in this increase bill specific) pattern by the system and method of the present invention. The patterned metallization is adhesively applied over a portion of the surface of the currency substrate. A protective layer is applied over the patterned layer.
In another aspect of the present invention, the currency bill is formed from a paper or other substrate. It can be formed by applying a release layer onto a polymer film and applying a substantially translucent protective coating over the release layer. This protective coating is metallized to form a metallized surface on the protective coating. A portion of the metallized surface is etched to form an item (or currency bill) specific pattern by supplying ink having an etchant or etchant-resistant mask material to an ink jet printhead. The metallized surface is ink jet printed with the desired pattern of ink having one of etchant or etchant-resistant mask material (followed by etching) for etching the metallized surface into an item specific pattern.
An adhesive is applied onto the patterned surface and the substrate engaged with the adhesive such that the release layer is broken and the protective coating and metallized layer having the item specific pattern is adhesively applied onto the substrate. The substrate could be a flexible paper member, such as a currency bill. The heat could be activated by applying heat to the adhesive.
A method aspect of the invention is also set forth for forming a pattern in a plain or holographic metallized film or hot stamp foil having metallized surface by supplying ink with an etchant or etchant-resistant mask material from an ink reservoir to an ink jet printhead having a plurality of ink jet channels and respective ink jets, each individually and digitally controlled by a controller. Ink is ejected through respective ink jets in a programmed manner. The method further comprises the step of controllably ink jet printing on the metallized surface a pattern of ink for etching either with the ink jet printed etchant or an etchant following printing of the etchant-resistant mask, the metallized surface into an item specific pattern.